All the fun stuff that comes with the holidays—fancy cocktails, rich food, late-night fêtes—can also come at a price: your sleep. While one night of lost zzz's is no biggie, two or three in a row creates an unhealthy and potentially dangerous deficit. "A sleep debt throws off your decision-making abilities and affects your performance at work and even while driving," says Joyce Walsleben, Ph.D., author of A Woman's Guide to Sleep (Random House) and associate professor of medicine at New York University School of Medicine. "Sleep is also very restorative to the immune system. Given all of our flu fears these days, you don't want to get run down." But you don't want to forgo the festivities either! And with our simple tricks for staying well-rested this season, you won't have to.

Sleep stealer: The three gingerbread man–tinis you had at the office party...or was it four?

Why it spoils your slumber: Alcohol makes you sleepy, but it's self-defeating, warns Walsleben: "You can't fall into deep, restorative dream sleep until you've metabolized the alcohol, and when you do, you get a rush of vivid dreams that can make sleep fitful or even wake you up," she says.

The fix: Go ahead, enjoy that snowball shooter—just do it early in the evening, and switch to virgin drinks three hours before bedtime to allow your body time to process the alcohol before your head hits the pillow.

Sleep stealer: Pumpkin pie, sugar cookies, Mom's famous fudge and all those other can't-say-no sweets

Why it spoils your slumber: Like alcohol, consuming sugary treats too close to bedtime can also result in a rude awakening. Refined sugar raises your blood glucose levels, which will suddenly drop two to three hours later, causing your body to sound the alarm that it's time to open your eyes and eat again, says Walsleben.

The fix: Dish up dessert at least an hour before you start to get ready for bed so your blood sugar levels have time to even out. If you're still hungry, Walsleben advises having a small snack that contains tryptophan, an amino acid that triggers your brain to produce sleep-bringing melatonin. Lean turkey, peanuts and lowfat cheese and milk are all good sources.

Why it spoils your slumber: Stress increases the flow of adrenaline and other neurotransmitters that alert the body and compete with the brain's ability to sleep, explains Walsleben. "And stress is particularly problematic for women because we're ruminators—we think and think about what's bothering us, and it keeps us up nights."

The fix: Keep a worry book, suggests Walsleben: In a notebook, jot down your worries on one side of a sheet of paper, then flip the page over and list possible fixes. When you're done, take steps to implement one of your solutions. "Knowing you've done something constructive during the daytime hours makes it easier to say 'I'm not worrying about this now' when you start to brood in bed," says Walsleben.

Sleep stealer: Midnight madness sales, the 9 P.M. showing of It's a Wonderful Life and the dozens of other temptations to stay up late.

Why it spoils slumber: Burning the midnight oil—and hitting the Snooze button to make up for lost shut-eye—can throw off your circadian rhythm, your body's internal clock that monitors your sleep-wake cycle. That makes it harder to drift off and wake up on time when your schedule returns to normal, leaving you progressively more sleep-deprived.

The fix: It's OK to sleep in a little bit, but try to maintain a wake-up time that's within an hour of what's typical for you, says Walsleben. If you're still dragging the next day, take a short nap, but keep it to 20 minutes. "It starts to make up for your sleep deficit and you'll feel a little better, but it won't disrupt your regular cycle."